1. Field of the Invention
This invention relates to improvements in and to automatic coffee machines, of the type comprising: a stationary cylinder wherein the coffee infusion is made; a lower piston vertically reciprocable within said cylinder between a coffee making lower position and an exhaused coffee dreg discharging upper position in line with the upper edge of said cylinder; an upper piston vertically reciprocable between a coffee making lower position within said cylinder and an upper position outside said cylinder, said upper piston being shiftable, in its upper position, from its alignment with said cylinder, in order to leave a coffee powder dose feeding funnel to be aligned with said cylinder; hot water feeding means into said cylinder between said pistons when in their coffee making positions; means for collecting the coffee infusion as obtained by passage of said hot water through said powdered coffee dose; and means for mechanically and sequentially controlling said piston motions and hot water feeding means.
2. Description of the Prior Art
An automatic coffee machine is disclosed in the U.S. patent application Ser. No. 28,090 filed on Apr. 9, 1979 and now U.S. Pat. No. 4,271,752, issued June 9, 1981, in the name of the same Applicants.
This known machine comprises side frame walls to which all operative components are fastenend or sustained. In particular the movements of upper and lower piston are herein mechanically controlled by a single motor operating on lever and cam systems. The lower piston is reciprocated by a two-lever system acted upon by two cams directly or indirectly controlled by said motor. The upper piston is slidably mounted on a vertical guide which in turn is fastened to an horizontally slidable block carrying said funnel. A L-shaped groove in said side walls has an horizontal length to guide the upper piston and funnel respectively into alignment with said cylinder, and a vertical length to guide the upper piston in its vertical reciprocating motion when in alignment with the cylinder.
A three lever systems controls the upper piston movements. The mechanical control of said operative components according to this known apparatus allows to avoid the costs of providing numerous microswitches, relays and consent means which impair the reliability of the apparatus. However, this mechanical control presents some difficulties in exactly phase controlling the movements of two pistons and funnel and particularly in exactly guiding the upper piston in its vertical motion so that it always maintains its axial alignment with cylinder in order to ensure a complete seal thereof also after numerous operating cycles.